1) Field of the Invention
The present invention relates to a bar code reader and, in particular, relates to a bar code reader that reads a bar code attached to a commodity.
2) Description of the Related Art
Products are managed by providing a bar code to the product and identifying the product by reading this bar code optically. Since the bar code labels can be prepared at a low cost by printing etc., by using such bar code labels, it is possible to reduce the management cost substantially.
The bar-code labels attached to the products are read using a bar code reader. Such a bar code reader generally includes an optical system like a laser reader, a charged coupled device (CCD) camera etc. The bar code reader receives light that is reflected from a bar code label, determines a pattern of the white lines and the black lines in the bar code from the optical power of the light reflected, and then decodes this pattern to obtain character data that is a pattern of numerals and characters. Such a bar code reader has been disclosed in, for example, Japanese Patent Application Laid-open Application No. 2000-251008.
The accuracy of reading of a bar code varies according to the position of receiving of the reflected light, i.e. the position of the photodiode. Thus, the position of the photodiode is an important factor that decides the accuracy.
Generally the conventional bar-code readers are equipped with a single circuit board and a photodiode that receives the light that is reflected from a bar-code label and an arithmetic unit that decodes the bar code are installed on this circuit board. When the photodiode is installed on the circuit board along with the arithmetic unit or other components, the positions where the photodiode can be installed are limited so that sometimes the photodiode cannot be installed in a suitable position that allows increased accuracy of reading. If the photodiode is not installed in the suitable position, there is a decline in the accuracy.